Embodiments relate to a semiconductor memory device, and more particularly, to a memory system including a nonvolatile memory.
A semiconductor memory device is a memory device which is fabricated at least partially from semiconductors such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), and the like. Semiconductor memory devices are generally categorized as either volatile memory devices or nonvolatile memory devices.
The volatile memory devices are usually characterized by the loss of stored data when power is interrupted or otherwise disconnected. Examples of volatile memory devices include certain types of random access memory (RAM) such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), and the like. The nonvolatile memory devices may retain stored contents even at power-off. Nonvolatile memory devices, on the other hand, are usually characterized by the retention of stored data when power is interrupted. Examples of nonvolatile memory include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable and programmable ROM (EEPROM), flash memory device (e.g., NAND type and NOR type), phase-change RAM (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM), ferroelectric RAM (FRAM), and the like.
Typically, the memory cell array of a semiconductor memory device extends in two dimensions with memory cells located at intersecting rows and columns Recently, however, semiconductor memory devices having a three-dimensional array structure have been developed to enhance integration densities.